The immune system of an individual declines markedly with advancing age. The ability of the older individual to combat bacterial and viral infections is therefore seriously reduced. The age-weakened immune system allows the occurrence of so called age-related diseases such as cancer, emphysema, maturity-onset diabetes, amyloidoisis, etc. With advancing age, not only does the body experience a decline in normal immune function, but in some individulas the immune system also becomes perverted, in that, in addition to failing to react appropriately to foreign agents, the system begins to attack the individual's own tissues. The perversion is manifested by the appearance of autoimmune diseases such as lupus erythematosus and rheumatoid arthritis. The objective of this research is twofold: 1. to determine the mechanisms responsible for the age-related decline in immune functions and 2. to find a treatment which will restore the normal immune function to old individuals and/or a treatment which will prevent the age-related deterioration from occurring.